Maximizing electrochemical energy conversion and storage performance of carbon aerogel with Co-Fe by tuning the synthesis method

The synthesis and application of cobalt-iron nanoparticles supported on 3D carbon aerogel are studied, with the expectation of improved performance in electrochemical energy conversion and storage systems. The structural and catalytic properties of the catalysts were optimized by applying the microwave irradiation method in both one-step and two-step manners. The synthesized catalysts were physically characterized using inductively coupled plasma-mass spectrometry, X-ray diffraction analysis, transmission electron microscopy, scanning electron microscopy with energy dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy to evaluate their metal loading ratios, crystallinity, morphology, textural properties, and surface chemistry. The results demonstrate that the synthesis method has a significant impact on the structural and catalytic properties of the materials, providing valuable insights into the design of advanced materials for sustainable energy applications. Among the synthesis methods employed, the one-step synthesis yielded material with improved electrochemical performance, achieving a specific capacitance of 644 F g⁻¹ at 5 mV s⁻¹ in 3 M KOH that further increased during continuous cycling. Co-Fe/CA-2 showed half that value, but still a promising result of 328 F g⁻¹. Dunn's analysis revealed that the studied materials store charge predominantly via a pseudo-faradaic mechanism. Galvanostatic charge/discharge cycling with Co-Fe/CA-1 was done both in two- and three-electrode set up with Faradaic efficiency as high as 93.8 % at 10 mA g⁻¹. The oxygen reduction reaction, essential for the operation of fuel cells and metal-air batteries, was observed to proceed predominantly via a favorable 4-electron mechanism at Co-Fe/CA-1, whereas Co-Fe/CA-2 exhibited mixed kinetics in 1 M KOH.